Example: Resolution of 1024X 768 (1024 screens dots going across and 768 from top to bottom)

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1 Monitors Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels or picture elements that are arranged in a rectangular form. Dots are usually very tiny and hard to notice them individually. The sharpness of the image depends upon the number of pixels (resolution). Example: Resolution of 1024X 768 (1024 screens dots going across and 768 from top to bottom) Graphic cards Graphics cards are hardware devices that plug into the motherboard and enable the computer to display images on the monitor. Graphics cards usually require the installation of software alongside the hardware. The software instructs the computer how to use the graphics card (Driver software) and also allows you to alter settings to change image quality and size. Page 1 of 14

2 Higher quality card can produce very clear graphics very quickly. Some computer games demand advanced display cards and high quality monitor screens. There are two kinds of viewing screen used for monitors. Cathode-Ray Tube (CRT) LCD Monitors / Flat- Panel Display Cathode-Ray Tube (CRT) Monitor The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity, or resolution. It takes more than one illuminated pixel to form whole character, such as the letter e in the word help. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically. Page 2 of 14

3 ADVANTAGES 1. Highest Resolutions: CRTs run at the highest pixel resolutions generally available. 2. Brightness and Contrast: Produce a very dark black and the highest contrast levels normally available. Suitable for use even in dimly lit or dark environments. 3. Color and Gray-Scale Accuracy: CRTs produce the very best color and gray-scale. 4. Best for rapidly moving or changing images. 5. Cost: CRTs are less expensive than comparable displays using other display technologies. DISADVANTAGES 1. Large in Size 2. High power consumption Flat-Panel Display Monitor The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls The flat-panel display is divided into two categories: Emissive Displays - The emissive displays are devices that convert electrical energy into light. Examples are plasma panel and LED (Light-Emitting Diodes). Non-Emissive Displays - The Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. Example is LCD (Liquid-Crystal Device) Page 3 of 14

4 Screen size LCD monitors are varying considerably in size and resolution. Example: Typical 15- inch screen might have a resolution of 1024 X 768 pixels and 30 inch screen 2560 X 1600 ADVANTAGES 1. Compact flat screen 2. Less power consumption. 3. Brightness: Produces very bright images due to high peak intensity. Very suitable for environments that are brightly lit. Page 4 of 14

5 Printers Printer is an output device, which is used to print information on paper (Hardcopy Output) There are two types of printers: Impact Printers Non-Impact Printers Impact Printers The impact printers print the characters by striking them on the ribbon which is then pressed on the paper. Characteristics of Impact Printers are the following: Very low consumable costs Very noisy Useful for bulk printing due to low cost There is physical contact with the paper to produce an image Non-impact Printers Non-impact printers print the characters without using ribbon. These printers print a complete page at a time so they are also called as Page Printers. These printers are of two types Laser Printers Inkjet Printers Characteristics of Non-impact Printers Faster than impact printers. They are not noisy. High quality. Support many fonts and different character size. Page 5 of 14

6 Laser Printers These are non-impact page printers. They use laser lights to make pattern of ink on a drum. This drum then transfers the ink to the paper. And finally heating process fuses the ink to the paper USES Businesses use laser printers almost exclusively because they have the reputation of being reliable while making a quality print product. Some common uses for laser printers include printing company stationery, making labels, and creating company fliers and brochures as printing is not messy due to smudging. ADVANTAGES Very high speed Very high quality output (often Black and White) Give good graphics quality Support many fonts and different character size Toner Cartridges last a long time and don t need to be replaced often. DISADVANTAGES Expensive. Cannot be used to produce multiple copies of a document in a single printing. Inkjet Printers Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper forming characters and pictures. Inkjet printers produce high quality output with presentable features. Colour printing is also possible. Some models of Inkjet printers can produce multiple copies of printing. Page 6 of 14

7 USES Home and small office use Used to print photographs (often produce colour prints) ADVANTAGES High quality printing High quality colour printing DISADVANTAGES Expensive as cost per page is high Messy due to ink spray and take some time to dry ink after printing( Smudgy) Slow as compared to laser printer Ink Cartridges do not last long and so are not suitable for large print jobs 3D Printer 3D printers allow us to print three dimensional solid objects in almost any geometrical shape. There are multiple methods to accomplish 3D printing but, essentially, a special resin is printed in layers until the object is completed. 3D printers follow digital CAD (Computer Aided Design) designs which provide the dimensions and shape of the object being printed. 3D printers are commonly used to print prototypes within industry; prototypes (small-scale versions of the real product) are built in order to find any product design flaws before it is mass produced. Page 7 of 14

8 A range of materials can be used when printing including metals, plastics, gold, fabric, acrylic and porcelain. USES OF 3D PRINTERS 1. 3D Printing In The Medical Industry 3D printing has been used to print organs from a patient s own cells. This means that patients may no longer have to wait a long time for donors in the future. In the past, hospitals implanted structures into patients made by hands. 2. 3D Printing In The Automotive Industry: Prototype car models and parts. 3. 3D Printing In The Aerospace Industry: Recently, NASA s rocket engine injector made from a 3D printer passed a major hot fire test. Page 8 of 14

9 Plotters Plotters are output devices used to print copies on a large sheet of paper. There are 2 different types of plotters-drum and flatbed. Plotters draw images on the page using colored pens which moved around the paper by a computer. USES OF PLOTTERS: Blueprints of building(plans/designs) Maps Giant posters and adverts(like those we see on billboards) Computer-aided design Page 9 of 14

10 Speakers Many everyday uses of computers require the user to listen to different types of sound. For example: o Listening to music album o Watching a movie o Browsing videos on YouTube o Multimedia encyclopedias In order for the computer to output these sounds it requires some sort of speaker system! Speakers can be connected directly to a computer or are built into the monitor or casing. Note: Most computers have small built in speakers to alert users when the do something wrong but these can only produce very basic sounds like beep Speakers are analogue and cannot output digital computerized sounds. Digital data from the computer must first be converted into analogue sound using a sound card. The analogue sound can then be output via the speakers and we can listen to it. Speakers can also be used alter the volume of the sounds. USES OF SPEAKERS Used to output sound from multimedia presentations (like famous speeches etc.). Used in home entertainment (surround sound etc.). Can be used by blind people to listen to words on the screen instead of reading. Page 10 of 14

11 Note: Special software called screen readers are also needed in order to convert the printed words into sound. Can be used to play download music files. Multimedia Projector or Data Projector These projects whatever appear on a computer monitor onto a very large screen so that large number of people can view it. Multimedia Projectors are usually controlled using a remote control. The remote control makes it possible to direct the presentations without the need to be at the computer. Multimedia projectors are often hung from the roof on special brackets. USES OF MULTIMEDIA PROJECTORS: Can be used for training presentations to allow the whole audience to see images from a single computer. Also used for large scale advertising of new products. Home cinema system where images from DVD s or televisions are projected on a large screen. Page 11 of 14

12 Control Devices Control devices are output devices which work together with sensors and commands from computers in order to control a process. Remember- Sensors gather measurable data from the environment and input it into the computer. They do not need any human involvement. Sensors typically gather data such as temperature, pressure, ph etc Data gathered by a sensor is input into the computer which then decides what to do with the data (processes it). Once the computer has decided what to do with the data it sends instructions to the control devices. The control devices then physically changes something in response to commands received from the computer. Consider this example: INPUT A burglar breaks the infrared light sensor on a security system. PROCESS- This data is sent to a small computer inside a security light The computer sends instructions to an actuator telling it to switch on the security light. OUTPUT- The actuator switches on the security light Page 12 of 14

13 ACTUATORS Actuators take instruction from the computer and then make the physical part of the process happen Actuators can also physically operate devices such as motors, pumps, switches and valves. USES OF CONTROL DEVICES The table below summarizes the main uses of different control devices. Remember- each of these control devices are switched on and off by an actuator Page 13 of 14

14 Types of control devices Used in: Advantages Actuators enable a computer to perform physical tasks in the real world. For example computers can control a central heating system or a mechanical digger. Do not need to employ people It is accurate and very quick Disadvantages These perform physical operations when instructed by a computer. This can be dangerous for people if their presence is not know by the computer If the computer malfunctions the system will not work The software for the control system is specialist and may cost a lot of money to develop Page 14 of 14